Re: [PATCH v2 0/5] Add the cat24c208 EDID EEPROM driver + new EDID capability

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Erling,

(CC'ing the linux-i2c mailing list and Srinivas, the maintainer of the
nvmem framework)

Thank you for the patches.

On Wed, Aug 03, 2022 at 09:58:45AM +0200, Erling Ljunggren wrote:
> This series adds support for the standalone cat24c208 EDID EEPROM i2c device.
> Usually EDID support is part of an HDMI receiver, but this is a standalone EEPROM.
> 
> Note that EEPROMs for EDIDs are not regular EEPROM devices, these are dual port
> devices that follow the VESA E-DDC standard.
> 
> Since this is a standalone device that does not capture any video a new
> V4L2_CAP_EDID_MEMORY capability is introduced to represent such devices.
> Note that such a device doesn't have to be an EEPROM, it can also be
> implemented using a microcontroller, for example. Hence the use of the generic
> word 'MEMORY'.

Why can't this be exposed as a nvmem device, like other types of eeproms
here ?

> The new capability uses the free bit 0x00000008. But we are running out of
> capability bits: only 0x40000000 and 0x00000008 are free at the moment.
> 
> There is one other capability V4L2_CAP_ASYNCIO (0x02000000) that is not used
> at all, it was never implemented. Wouldn't it be better to define
> V4L2_CAP_ASYNCIO to 0, mark it as obsolete, and instead reuse it for this
> V4L2_CAP_EDID_MEMORY capability?
> 
> v2:
>  - fix dt binding example
>  - rename i2c client variables in data struct
>  - fix include: of_device.h -> mod_devicetable.h
>  - Sorted makefile
>  - used define EDID_OFFSET_EXT_FLAG instead of magic number
>  - removed of_match_ptr
>  - added bus_info
>  - remove unneeded headers
>  - add depends on OF to Kconfig
> 
> Erling Ljunggren (4):
>   media: videodev2.h: add V4L2_CAP_EDID_MEMORY
>   media: docs: Add V4L2_CAP_EDID_MEMORY
>   dt-bindings: media: add cat24c208 bindings
>   media: v4l2-dev: handle V4L2_CAP_EDID_MEMORY
> 
> Jonathan Selnes (1):
>   media: i2c: cat24c208: driver for the cat24c208 EDID EEPROM
> 
>  .../bindings/media/i2c/onnn,cat24c208.yaml    |  40 ++
>  .../userspace-api/media/v4l/biblio.rst        |  11 +
>  .../media/v4l/vidioc-querycap.rst             |   7 +
>  .../media/videodev2.h.rst.exceptions          |   1 +
>  MAINTAINERS                                   |   7 +
>  drivers/media/i2c/Kconfig                     |   9 +
>  drivers/media/i2c/Makefile                    |   1 +
>  drivers/media/i2c/cat24c208.c                 | 421 ++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-dev.c            |   8 +
>  include/uapi/linux/videodev2.h                |   1 +
>  10 files changed, 506 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/i2c/onnn,cat24c208.yaml
>  create mode 100644 drivers/media/i2c/cat24c208.c

-- 
Regards,

Laurent Pinchart